Large-Area Microphone Array for Audio Source Separation Based on a Hybrid Architecture Exploiting Thin-Film Electronics and CMOS

Abstract

We present a system for reconstructing-independent voice commands from two simultaneous speakers, based on an array of spatially distributed microphones. It adopts a hybrid architecture, combining large-area electronics (LAE), which enables a physically expansive array ( ${>} 1\text{ m}$ width), and a CMOS IC, which provides superior transistors for readout and signal processing. The array enables us to: 1) select microphones closest to the speakers to receive the highest SNR signal; 2) use multiple spatially diverse microphones to enhance robustness to variations due to microphones and sound propagation in a practical room. Each channel consists of a thin-film transducer formed from polyvinylidene fluoride (PVDF), a piezopolymer, and a localized amplifier composed of amorphous silicon (a-Si) thin-film transistors (TFTs). Each channel is sequentially sampled by a TFT scanning circuit, to reduce the number of interfaces between the large-area electronics (LAE) and CMOS IC. A reconstruction algorithm is proposed, which exploits the measured transfer function between each speaker and microphone, to separate two simultaneous speakers. The algorithm overcomes 1) sampling-rate limitations of the scanning circuits and 2) sensitivities to microphone placement and directionality. An entire system with eight channels is demonstrated, acquiring and reconstructing two simultaneous audio signals at 2 m distance from the array achieving a signal-to-interferer (SIR) ratio improvement of ${\sim} 12\text{ dB}$ .